LD modules are in wide use that include a laser diode and an optical fiber and that are configured to cause a laser beam outputted from the laser diode to enter the optical fiber. To increase the reliability of such LD modules, it is necessary to increase the mean time to failure of the laser diode.
Examples of known techniques for increasing the mean time to failure of laser diodes include the respective techniques disclosed in Patent Literatures 1 and 2. The technique disclosed in Patent Literature 1 is intended to prevent or reduce catastrophic optical damage (COD) by treating an end surface of a laser diode with a treatment liquid that serves to prevent or reduce the surface level. The technique disclosed in Patent Literature 2 is intended to decrease the light confinement coefficient (r factor) of an active layer by dispersing the vertical light density.